JP2010199342A - Solar cell, module, and photovoltaic power generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the power generating performance of a solar cell by collecting and supplying a direct light beam which is cut off by a light receiving surface electrode to be lost to a power generating element surface so as to improve the performance of the solar cell. <P>SOLUTION: The power generating performance is improved by configuring the solar cell to have directivity taking the latitude of an installation place and an altitude of the sun into consideration and also to collect the direct light beam which is cut off by the triangular light receiving surface electrode to the power generating element surface through specular reflection on front and rear slopes of the light receiving surface electrode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an improvement in the performance of a solar cell.

Various methods have been proposed to improve the performance of solar power generation, such as improving the performance of the power generation element itself, and devising the surface shape with an anti-reflection film to effectively use the light incident on the power generation element. In the solar cell having a structure in which an electrode is provided on the surface of the power generation element, there is a disadvantage that the direct light ray is blocked by the surface electrode and the performance is lowered. In order to improve this inconvenience, a method of concentrating the light beam in advance by the condensing unit to secure a space and arranging the light receiving surface electrode in this space can be considered. .
Japanese Patent Application No. 2008-309186 Solar Lens JP-A-2001-189487 Concentrator and Concentrating Solar Cell Module

  The method of Patent Document 1 is a solar lens in which an inverted trapezoidal solar lens is formed of a transparent material and condenses incident light on a light exit surface by total reflection, but the solar lens is disposed between the electrodes of the solar cell. When the electrodes are arranged in the gap, there is no problem in that all of the incident light can be effectively supplied to the power generation element, but in order to ensure durability, the solar cell and the solar lens When the whole is sealed as a solar cell module with a transparent filler in a transparent substrate, there is a problem that the space between the solar lenses disappears and the light cannot be condensed by total reflection.

  Further, the method of Patent Document 2 is a method of condensing light by a combination of specular reflection and total reflection by a reflecting film. However, since directivity is not considered in the direction of incident light, reflection is performed as shown in FIG. It is necessary to take a very large inclination angle of the film, which makes it difficult to manufacture in shape and has a disadvantage of low light collecting performance. The challenge is to improve the performance by developing a concentrating solar cell that can condense all of the sunlight that strikes the light receiving surface electrode portion onto the power generating element surface and has a simple shape.

  By providing directivity to the solar cell and condensing the direct ray blocked by the light receiving surface electrode of the solar cell on the power generating element surface by the mirror reflection of the light receiving surface electrode itself, the power generation performance is improved and the It solves the problem.

  In conventional solar cells, more than 10% of the light-receiving surface is occupied by the light-receiving surface electrode, and there was a corresponding loss of incident light. However, since the loss can be almost eliminated, the power generation performance can be improved. effective.

  FIG. 2 shows a cross section of a flat plate solar cell 1 according to the present invention, in which 2 is a power generation element, 3 is a large number of elongated light receiving surface electrodes that are electrically connected to the power generation element and arranged at equal intervals, It is a back electrode. In addition, the cross section of the light receiving surface electrode is a triangle having a bottom surface that is in contact with the power generation element, and includes a front slope 5 and a rear slope 6. The front slope has a tilt angle α1 and the rear slope has a tilt angle α2. is doing. When assembled as a solar cell module, the entire structure is held between the transparent substrate 7 and the transparent filler 8. Reference numeral 9 denotes a light incident surface of sunlight corresponding to the tip of the light receiving surface electrode. Reference numeral 10 denotes a collecting electrode arranged at right angles to the light receiving surface electrode to electrically connect all the light receiving surface electrodes. The light receiving surface electrode and the collecting electrode are integrally formed in a comb shape with a conductive material such as silver. ing. Reference numeral 11 denotes a back plate made of resin or the like.

  Note that the front and rear slopes of the light-receiving surface electrode formed in a triangle are intended to act as reflecting surfaces. Therefore, if the current collection performance is not degraded, the tip of the triangle may have a low conductivity. You may form with cheap materials with high reflective performance, for example, aluminum, a synthetic resin, etc.

  Since the solar cell of the present invention has directivity, in the following description, it is assumed that the front slope is facing south and is installed horizontally, and the slope and the inclination angle of the light beam are inclined with respect to the vertical plane unless otherwise specified. It shall be indicated in angle.

  Sunlight incident on the light entrance surface is refracted and travels according to the refractive index of the transparent substrate or transparent filler, but in order to condense all incident light rays onto the power generation element surface, light rays that directly strike the power generation element surface In addition, it is necessary to direct the light rays hitting the front and rear slopes to the power generation element surface by specular reflection.

  In addition, an antireflection film is often provided on the surface of the power generation element, but it is desirable to set the angle differences α3 and α4 with respect to the rays reaching the power generation element surface to be equal to or less than the critical refraction angle of the constituent material. This is because if there is a gap between the power generation element surface and the transparent filler, the light beam is totally reflected and inverted and dissipated.

  For this purpose, the inclination angle α2 of the rear slope is set so that the sunlight with the highest altitude incident on the tip of the rear slope reaches the power generating element surface by specular reflection, and the minimum height incident on the tip of the front slope is set. It is necessary to set the inclination angle α1 of the front slope so that the sunlight rays reach the power generation element surface by specular reflection, and angle differences α3 and α4 with respect to the light beam reaching the power generation element surface are filled between the light receiving surface electrodes. It is desirable to set it to be equal to or less than the critical refraction angle of the filler. With such a setting, it is possible to concentrate all the sunlight from the maximum altitude to the minimum altitude on the power generation element surface.

  The height of the light receiving surface electrode is such that the light beam e1 reflected by the rear slope directly hits the front slope and is reversed and does not dissipate from the light entrance surface, and the light beam e2 reflected by the front slope strikes the rear slope directly. It may be set to a range that does not. This can be solved by setting the distance between the light receiving surface electrodes sufficiently wide. However, if the distance is too wide, the performance of the solar cell will be reduced. The overall performance can be improved by reducing the distance between the electrodes.

  As described above, by giving directivity to the solar cell in consideration of the variation range of the solar altitude and the installation direction, it is possible to easily collect the sunlight. For example, in the case of Tokyo, the maximum altitude is 78 degrees on the summer solstice and the minimum altitude is 31 degrees on the winter solstice at noon. Can be collected and supplied to the power generation element.

  FIG. 3 shows a concentrator disclosed in Patent Document 2, in which the condensing magnification is small and the reflection film has a simple shape that requires only a small inclination. 12 is a collector body made of a transparent material having a refractive index larger than that of air, and 13 and 14 are reflection films, which collect the light incident from the light incident surface 15 and condense it on the light output surface 16, Since directivity is not considered in the direction of incident light, it is necessary to incline the reflective film extremely greatly. In the case of forming with a transparent material having a refractive index of 1, 5 as a specification with a small inclination angle, the ratio of the light incident surface to the light output surface is 1, 5 and the thickness is 0.5 times the length of the light output surface. However, it is considered that the manufacturing is extremely difficult because of the shape in which the front and rear reflection films overlap with the light exit surface, and the practicality is considered to be low. On the other hand, if the tilt angle is set to be small, the area difference between the light incident surface and the light exit surface becomes smaller, and the electrode space cannot be secured.

  FIG. 3 shows a ray path with rays corresponding to the maximum altitude and the minimum altitude. Even at the same altitude, depending on the incident position, the light reaching the light exit surface will be totally reflected, but if the surface reflective film of the solar cell is directly connected to the light exit surface, it will follow a more complicated light path. Become. In the solar cell of the present invention having a triangular light-receiving surface electrode, it is not necessary to specially equip such a concentrator with a gap, but rather it is structurally stable because there is no gap, since the whole can be sealed with a filler. It is possible to prevent deterioration in performance due to oxidation.

  FIG. 4 shows the shape of the light-receiving surface electrode and the condensing state by the path of the incident light when it is assumed that the solar cell is inclined to the south. Ray path of maximum altitude ray m1 when condensing sunlight with a critical angle of refraction of 42 degrees (refractive index of about 1.5) and a maximum altitude of 85 degrees and a minimum altitude of 5 degrees. The minimum height ray m2 is drawn according to the actual situation. Rays below the maximum altitude are in the middle ray path between m1 and m2.

  As described above, the solar cell of the present invention has directivity in the direction in which light can be collected from the shape of the light-receiving surface electrode and can collect light rays from the front slope direction. Light rays other than the incident light rays that reach the power generation element surface can hardly be collected. By limiting the light collection range of sunlight to the light of the maximum altitude to the minimum altitude according to the latitude, a highly practical condensing performance is ensured.

  Condensation performance is slightly reduced, but product integration can be achieved by setting specifications with a wide range of latitudes that can be used. For example, considering the difference in latitude from Okinawa to Hokkaido, solar cells that correspond to the maximum altitude in Okinawa and the minimum altitude in Hokkaido can be used throughout Japan. Note that the maximum altitude and minimum altitude periods are extremely limited throughout the year, so by setting the altitude fluctuation range small, the slope of the front and rear slopes of the light-receiving surface electrode becomes gentle and easy to manufacture. It becomes.

  When solar cells are installed in consideration of the direction of the sun, the light rays entering from an oblique direction, such as sunlight from the southeast, are decomposed into two rays, one traveling from the front slope in the north-south direction and the other traveling in the east-west direction. Although it can be considered, the light beam traveling along the light receiving surface electrode is reflected by the trapezoidal slope surrounded by the adjacent light receiving surface electrodes and reaches the power generating element surface.

  At times when the altitude close to sun rises is low, the sun rays shine from a direction in the range of about 30 degrees from the east-west axis depending on the season. These rays can be condensed on the power generation element surface in the same manner. However, in the limited time zone where the sun rises and falls before and after the summer solstice, it is considered that only a part of the light beam is lost without being collected because the reverse sun rays from the east-northeast or west-southwest are incident.

  FIG. 5 shows a solar power generation device including a solar cell module having directivity, in which the entire slope of the solar cell is disposed with the front slope of the solar cell facing south. In the case of installation in the southern hemisphere, the solar cell is inclined northward and the front slope is installed northward, but the optimum inclination angle of the module varies depending on the latitude.

  Thus, the solar cell of the present invention focuses incident light blocked by the light receiving surface electrode by mirror reflection on the power generating element surface using the inclined surface of the triangular light receiving surface electrode, and the installation direction has directivity, It has an extremely simple shape and can improve the performance comprehensively, and has a high practicality.

It is a perspective view of a solar cell. It is sectional drawing of a solar cell. It is explanatory drawing of the collector of patent document 2. FIG. It is sectional drawing of the inclined solar cell. It is a perspective view of the solar power generation device which installed the solar cell module facing south.

DESCRIPTION OF SYMBOLS 1, Solar cell 2, Electric power generation element 3, Light-receiving surface electrode 4, Back surface electrode 5, Front slope 6, Rear slope 7, Transparent substrate 8, Transparent filler 9, Light entrance surface 10, Collector electrode 11, Back plate

Claims (4)

  When the cross section of the light-receiving surface electrode of the solar cell is formed in a triangle whose surface is in contact with the power generation element and is arranged so that sunlight rays enter from the direction of the front slope of this light-receiving surface electrode, The slope of the rear slope is set so that the incident maximum solar radiation reaches the power generation element surface by specular reflection, and the minimum altitude solar light incident on the front slope tip reaches the power generation element surface by specular reflection. A solar cell characterized in that the inclination of the front slope is set as described above.   The solar cell according to claim 1, wherein the front and back slopes are set so that an angle difference with a light beam reaching the power generating element surface is equal to or less than a critical refraction angle of the transparent filler constituting between the light receiving surface electrodes. A solar cell.   A solar cell module comprising: a plurality of solar cells according to claim 1 arranged in a plane with the same orientation of the light receiving surface electrodes, and the solar cells being electrically connected to each other.   4. A solar power generation apparatus, wherein the solar cell module according to claim 3 is disposed such that a front slope of a light-receiving surface electrode faces southward.

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